Tubular reactor for carrying out endothermic and exothermic reactions with forced circulation

ABSTRACT

A tubular reactor with forced circulation of a heat transfer medium which flushes the outside of the reaction tubes in axial direction, the heat transfer medium being supplied to, and withdrawn from, the reactor wall uniformly through circular pipelines, and particularly the constructional shape of deflecting guide plate means arranged transversely to the direction of flow and having annular openings around the reaction tubes for uniform flow towards all the tubes of the nest of tubes.

United States Patent [72] Inventors Friedrich Lorenz Neustadt, Weinstrasse; Joachim Wagner, Ludwigshafen, Rhine; Dieter Bettermann, Waldsee; Walter Mann, Lampertheim; Johann Heinrich Walter, Ludwigshafen, Rhine, Germany [21 Appl. No. 757,957

[22] Filed Sept. 6, 1968 [45] Patented Mar. 2, 1971 [73] Assignee Badische Anilin & Soda Fabrik Aktiengesellschaft Ludwigshafen, Rhineland-Pfalz, Germany [32] Priority Sept. 6, 1967, Sept. 23, 1967 [33] Germany I P 16 01 162.4 and P 16 01 163.5

[54] TUBULAR REACTOR FOR CARRYING OUT ENDOTHERMIC AND EXOTHERMIC REACTIONS WITH FORCED CIRCULATION 6 Claims, 10 Drawing Figs.

[52] U.S.Cl 165/159, 165/107,165/160 [51I Int. Cl F28f9/22 [50] Field ofSeareh 165/107; 165/159, 160

[56] References Cited UNITED STATES PATENTS 827,479 7/1906 Towne 165/159 2,185,928 1/1940 165/159X 2,805,049 9/1957 165/159 3,351,131 11/1967 Berthold 165/159 3,398,789 8/1968 Wolowodiuk et al 165/1 59X 3,434,807 3/1969 lbing et a1. 165/159X Primary Examiner-Albert WrDavis, Jr. AttarneyJohnston, Root, OKeefe, Keil, Thompson 8:.

Shurtleff H H N H II PATENTEDHAR 2197! 3,566,961

SHEET 1 OF 4 INVENTORS:

' FRlEDRlCH LORENZ JOACHIM WAGNER DIETER BETTERMANN WALTER MANN JOHANN HEINRICH WALTER PATENTEUHAR 21971 8566861 sumznra 000 .00 9 0000 .ooQQo ooouoo 00 INVENTORSI FRIEDRICH LORENZ JOACHIM WAGNER DIETER BETTERIMANN WALTER MANN JOHAgl N HEINRICH WALTER PATENTEDHAR 21971 3566;961 sumanw IINVENTORSI FRIEDRICH LORENZ JOACHIM WAGNER DIETER BETTERMANN WALTER MANN JOHABNN HEINRICH WALTER www z 6 ATT'YS PATENTED m 2 IQYI IlNVENTORS FRIEDRICH LORENZ JOACHIM WAGNER DIETER BETTERMANN WALTER MANN SHEET U? 4 ATT'YS TUBULARREACTOR FOR CARRYIN G OUT ENDOTHERMIC AND EXOTHERMIC REACTIONS WITH FORCED CIRCULATION The invention relates generally to apparatus for chemical plant having a nest oftubes and particularly to a reactor suita-' ble for carrying out endothermic and exothermic reactions, in the tubes of which the reaction takes place and in which a heat transfer medium impinges'on the outside of the tubes in axial direction, delivery of equal amounts to each individual tube being ensured by various constructional means.

Reaction apparatus of great capacity is already known having a nestof tubes arranged around a central guide tube in which the medium flushing the tubes'iscirculated by a convey ing meanslocated in the guide tube. The guide tube also contains a Heat exchanger whose connections are taken out from the apparatus in the central zone. The-nest of tubes to be impinged onoften contains several thousand individual tubes'and special demands are made on their welds. The use of highly ef fective catalysts in such apparatus means that thethroughput of medium to be conducted by the conveyingmeans through the central guide tube necessary to ensure conveyance of heat has to be increased considerably. The heatexchange through the outer casing of the apparatus is negligibly small. This fact has necessarily led in the design of reactors of 'highercapacity to an increasein the cross section of the guide tube withthe heat exchanger situated therein and consequently to a smaller cross-sectional area for the nest of tubes. Since, ontl'le other hand, the maximum diameter of the apparatus is limited by its transportability, the aim has been to achieve a maximum output for a givenv maximum diameter of reactor. For the prior art method of constructionhaving a central guide tube, ther'e is therefore a constructional limit set which cannot be exceeded.

In other connections heat exchange apparatus having. forced circulation of a heat exchangingmedium is known in. which the conveying means is located outside the nestof tubes. Iii this apparatus the most uniform impingement possi= ble on the nest of tubes which is required for reactions in reactors having nests of tubesin the sense of the desired course of the reaction and a maximum yieldor in product quality is, however, left out of consideration. Each individual tube ina reactor at any given cross section'of the nest of tubes should be impinged on by circulating or heat transfer media of the same temperature and velocity. This requirement is all the more difficult to meet because the temperature in the in dividual tubes over a prolonged periodof operation changes owing to the unavoidable aging of the catalyst.

It is therefore the object of this invention to provide areactor having a nest of tubes suitable for carrying out exothermic and endothermic chemical reactions which, havingregard to the possibility of transportation with maximum productivity of the reaction, ensures a uniform impingement on each individual tube of heat transfer media. at the same temperature, amount and speed. Moreover, the energy requirement of the conveying means which should be easy to maintainfor the heat transfer medium should be a minimum.

For the solution of the problem the followingpoint's must be considered:

Heat transfer is in fact higher in the caseof tubes with transverse flow than in the case of axial flow, but the essential requirement of the same temperature of the heat transfer medium at the same point in each individualtube can only be fulfilled with an adequately uniform axial flow owing to the course of the reactionstriven for in the interior of the tubes.

In the constructional solution of the problem posed, starting from a tubular reactor of prior art design with forced circulation of the medium flushing the outside of the tubes by a conveying means located outside the reactor, the required axial flow along the tubes iscapable of being influenced by guide plates arranged transversely to the tubeaxis.

According to this invention such an apparatus for fulfilling the requirements mentioned aboveis improved by surrounding the casing of the tubular reactor (or nested tube reactor) bya circular line for the supply, and another circular line for the withdrawal, of the heat transfer medium supplied by the conveying means located externally, the reactor casing at the nest of tubes are provided with orifices of constant size and. the thickness of the guide plate becomes less from the outside.

to the inside of the same;

According to another feature of the invention, the crosssectional area of the orifices in the guide plates may increase from the outside towards the inside.

Anotherf'eature of the invention may, consist in the provision of additional annular guide plates besides the guide plates which extend over the whole cross section of the nest of tubes.

. Other features of the invention will be evident from the fol lowing detailed description in conjunction with the drawings.

FIG; I is a diagrammatic sectional elevation of a nested tube reactor according to this invention;

FIG. 2 is a section taken on the line A.-A in FIG. 1;

FIGS. 3 and 4 are details showing tubes surrounded by guide plates having appropriate orifices;

- FIG. 5 is a diagrammatic sectional elevation of a further embodiment of nested tube reactor according to the invention;

' FIG. 6 is a section taken on the line B-B'in FIG. 5;

' FIG. 7 is a partial vertical section illustrating in greater.

detail one modification of the nested tube arrangement passing through guide plates shown only diagrammatically in FIG. 5;

FIG. 7A is a partial horizontal section taken on the line A-A of FIG; 7;

FIG. 8 is a partial vertical section similar to FIG. 7 but illustrating another modificationof the nested tube arrangement passing through a different set of guide plates; and

FIG. 9 is a partial'horizontal section similar to FIG. 7A to illustrate guide plates containing additional orifices or bores distributed between the orifices around individual tubes.

Referring to FIGS. 1 and 2, the nest 1 of tubes filled with. catalyst occupies almost all of the space enclosed by the castion enclosed by the casing 2, contains aplurality of orifices 10 of such dimensions that theheat transfer medium-flows at a velocity which is the same over the entire cross section of the nest of tubes, along the nest of tubes 1 to the upper guide plate 6. After having passed through the orifices 10 in the guide plate 6, the heat transfer medium passes through openings 12 in the casing 2 into the'upper circular line 7 and thence is returned to the cooler 3.

The openings 9 in the casing 2 at the level of the circular line 4 are of such size that the sum of the pressure lossesfrom flowing into the circular line and the: passage through the openings is the same for all the stream threads. In thisway the heat transfer medium is distributed uniformly over the whole extent of the casing 2 and its uniform radical entryinto the nest of tubes is ensured. These crossesectional dimensions derived from the measurable pressure losses also hold good for the egress of the heat transfer medium through theupper openings 12 of the casing 2 into the circular line 7. The supply and withdrawal of heat transfer medium through the circular lines 4 and 7 located outside the casing 2 is particularly favorable, because the largest areas of passage between the guide plates 5 and 6 and the tube plates 8 and 14 are available for the largest amounts of heat transfer medium flowing.

The orifices 10 in the guide plates 5 and 6 are of such a size that the sum of the pressure losses from the transverse flow through the nest of tubes before and after passage through the guide plates 5 and 6, and the divided flow in the orifices is constant for stream threads situated farther out or farther in. Equal amounts of heat transfer medium then flow through equal areas of nestedtube cross section between the guide plates 5 and 6. If flat guide plates 5 and 6 are used, the same pressure loss is obtained for each stream thread from the transverse flow inwards and from the flow through the orifices 10, when the individual areas of the orifices are either made greater from the outside to the inside to a calculated extent or (with orifices of equal size) when the thickness of the guide plates is made greater at the outside than in the neighborhood of the axis of the reactor or in the central region.

On the other hand, the distance of the guide plate 5 from the adjacent tube plate 8 may be such in a radial direction that the pressure loss of the transverse flow through the nest of tubes provided between these elements is constant for each stream thread inwards up to the orifices 10. It follows from this that this distance may have to be made different in the radial direction. Usually a greater distance is necessary at the outside than in the central region of the nest of tubes. Approximately the same result can be achieved if the tubes are arranged in such a way that the distance between them increases towards the center of the nest of tubes. In this embodiment the tube separation is smaller at the outside than in the center of the nest of tubes. By apportioning the distance, the orifices 10 in the guide plate 5 may be made the same size at every point of the cross section of the nest of tubes so that the flow of heat transfer medium along the tubes 13 is the same at every point. This provision for the distance between the guide plate and the upper tube plate 11 holds good in an analogous way for the egress of the heat transfer medium through the orifices 10 in the upper guide plate 6.

In a practical embodiment having different distances between the guide plates 5 and 6 and the adjacent tube plates 8 and 11, the guide plates are shaped either conically or hemispherically. Additional flat guide plates with orifices 10 may be installed in the heat exchanger over the length of the tubes between the shaped guide plates 5 and 6 in order if necessary to influence again the desired axial flow along the tubes.

FIGS. 3 and 4 show advantageous shapes for the orifices 10 in the guide plates 5 and 6. These orifices 10 are preferably designed so that interstices are formed around the individual tubes 13 of the nest of tubes 1. The size of the area of the interstice is regulated according to the position of the tube in the whole cross section of the nest of tubes so that the required pressure loss is achieved at this position.

If the flow of heat transfer medium requires orifices of such size that either the lands of material remaining between the individual interstices is no longer adequate for the strength of the guide plate or the required orifice area can no longer be achieved by interstices around individual tubes, the orifice is designed so that (as shown in FIG. 4) they completely surround two or more adjacent individual tubes as a group.

Other constructional embodiments as shown in FIGS. 5, 6, 7, 7A, 8 and 9 for equalizing the different pressure losses at individual tubes situated on the outside and lying in more central positions are possible within the scope of this invention. In addition to guide plates 5 and 6 occupying the whole cross section of the nest of tubes and having all the orifices of the same size, it is possible by this equalization to provide further flat guide plates 5, 5 and 6, 6 having a smaller total area and having orifices still of the same size. Preferably, these additional guide plates having smaller areas are constructed as annular surfaces having an appropriate number of orifices 10, the outer diameter of these guide plates being about equal to the inner diameter of the casing of the casing of the apparatus.

When the stream threads pass through other orifices 10 located nearer the perimeter, the same pressure loss results as with longer stream threads in the central region of the nest of tubes.

This embodiment of the reactor is shown diagrammatically in FIGS. 5 and 6 and in a more detailed vertical or horizontal section in FIGS. 7, 7A and 8.

The cross sections of the openings 9 at the level of the circular inlet line 4 and, correspondingly, those of the openings 12 at the level of the circular outlet line 7, in order to equalize different pressure losses on the way from the conveying means 3a to the entry into the nest of tubes, advantageously increase from entry or outlet point of the heat transfer medium into (or out from) the circular line up to the opposite side of the periphery of the casing.

As shown in FIGS. 7, 7A and 8, a guide plate 5 arranged near to the lower tube plate 8 which occupies the whole of the cross section of the nest of tubes 1 and other guide plates 5' and 5" (preferably parallel thereto) which are constructed as annular plates, have a number of orifices l0, l0 and 10" of equal size which are so arranged that the heat transfer medium flows along the nest of tubes 1 to the upper guide plates 6, 6' and 6" with a velocity which is the same across the whole cross section of the nest of tubes. The orifices 10, 10' and 10 are advantageously not only equal in area but of the same geometrical shape, i.e., made congruent. After the heat transfer medium has passed through the orifices of the guide plates 6, 6' and 6", it passes through openings 12 in the casing 2 into the upper circular line 7 and thence is returned to the conveying means 3a (see FIGS. 5 and 6).

The openings 9 in the casing 2 at the level of the circular line 4 are of such size that the sum of the pressure losses from the flow in the circular line and passage through the openings is the same for all stream threads. In this way the heat transfer medium is distributed over the whole extent of the casing 2 and its uniform radial entry into the nest of tubes is ensured. The same is true of the dimensions of the cross section derived from the measurable pressure loss for the egress of the heat transfer medium through the upper openings 12 of the casing 2 into the circular line 7.

The orifice 10, 10 and 10" in the guide plates 5,5 and 5" and 6, 6 and 6" are of such size that the sum of the pressure losses from the transverse flow through the nest of tubes 1 and from the flow through the orifices 10, 10 and 10" is the same for all stream threads. Equal amounts of heat transfer medium then flow through the same areas of nested tube cross section between the guide plates 5, 5 and 5" and 6,6 and 6".

Adaptation to the different pressure losses across the whole of the nest of tubes may also be carried out in this embodiment by varying the effective length of the orifices 10 following each other at the individual tubes. In practice this is effected, the cross-sectional areas of the orifices 10 being of equal size, by making the total thickness of all the guide plates smaller in stages from the outside towards the center. For example, as shown in the specific embodiments of FIGS. 7, 7A and 8, the annular guide plates 5' and 5 and 6' and 6" may be provided at increasing inward distances away from each of their corresponding guide plates 5 and 6, respectively, (as shown in FIGS. 7 and 7A) or else these additional guide plates may be welded direct to the guide plates 5 and 6 (as shown in FIG. 8). The stagewise reduction in the thickness of the plates is again such that the sum of the pressure losses from the transverse flow through the nest of tubes 1 and the flow through the orifices 10 is equal for all stream threads.

When, in such an embodiment of a nested tube heat exchanger having orifices 10 of equal size in the guide plates 5 and 6 in the central region of the nest of tubes (regarded as a whole), larger cross-sectional areas of the orifices are necessary to equalize measured pressure losses, additional orifices 10a as shown in FIG. 9 (preferably bores of small cross-sectional area) may be provided between the orifices l0 surrounding the individual tubes 13 as circular rings. In this case the guide plates 5 and 6 have an increasing number of orifices 10a per unit of area from the outside to the center.

We claim:

' 1. In a nested tube reactor for carrying out endothermic and exothermic reactions with forced circulation of a heat transfer medium flushing the tubes from a conveying means located externally of the heat exchanger formed by the reactor tubes enclosed by a casing having inlet and outlet openings around its periphery in communication with one circular line for the supply and another circular line for the withdrawal of said heat transfer medium which is circulated by said conveying means, the improvement in combination therewith which comprises a perforated guide plate means arranged substantially transversely to the axes of the tubes to extend over the cross section of the reactor and containing orifices of equal size surrounding the tubes while the thickness of said guide plate means is varied from the outside to the center of the reactor to provide a corresponding variation in the effective length of the orifices such that the heat transfer medium flows uniformly over the cross section of the reactor.

2. A nested tube reactor as claimed in claim 1 wherein said guide plate means is composed of at least one flat plate extending across the entire cross section of the reactor and additional flat plates of smaller total area arranged so that the effective length of the orifices of equal size in all plates is varied stagewise from the outside to the center of the reactor.

3. A nested tube reactor as claimed in claim 2 wherein said additional guide plates are designed as annular plates having an external diameter approximately equal to the internal diameter of the reactor casing.

4. A nested tube reactor as claimed] in claim 2 wherein said tubes are mounted at either end and held by tube plates, a fiat guide plate extending across the entire cross section of the reactor is positioned adjacent to and at an inwardly spaced distance away from each of said tube plates along the tube axes, and a plurality of additional annular flat guide plates are provided at increasing inward distances away from each of said first-named guide plates, the totall area of each additional annular guide plate associated with one of said first-named guide plates becoming progressively smaller than the preceding guide plate in a direction inwardly along the tube axes.

5. A nested tube reactor as claimed in claim 1 wherein the effective length of the orifices in said guide plate means increases from the center to the outside of the reactor.

6. A nested tube reactor as claimed in claim 5 wherein said guide plate means contains additional orifices between the orifices surrounding the tubes, the number of said additional orifices per unit area of said plate means increasing from the outside to the center of the reactor 

1. In a nested tube reactor for carrying out endothermic and exothermic reactions with forced circulation of a heat transfer medium flushing the tubes from a conveying means located externally of the heat exchanger formed by the reactor tubes enclosed by a casing having inlet and outlet openings around its periphery in communication with one circular line for the supply and another circular line for the withdrawal of said heat transfer medium which is circulated by said conveying means, the improvement in combination therewith which comprises a perforated guide plate means arranged substantially transversely to the axes of the tubes to extend over the cross section of the reactor and containing orifices of equal size surrounding the tubes while the thickness of said guide plate means is varied from the outside to the center of the reactor to provide a corresponding variation in the effective length of the orifices such that the heat transfer medium flows uniformly over the cross section of the reactor.
 2. A nested tube reactor as claimed in claim 1 wherein said guide plate means is composed of at least one flat plate extending across the entire cross section of the reactor and additional flat plates of smaller total Area arranged so that the effective length of the orifices of equal size in all plates is varied stagewise from the outside to the center of the reactor.
 3. A nested tube reactor as claimed in claim 2 wherein said additional guide plates are designed as annular plates having an external diameter approximately equal to the internal diameter of the reactor casing.
 4. A nested tube reactor as claimed in claim 2 wherein said tubes are mounted at either end and held by tube plates, a flat guide plate extending across the entire cross section of the reactor is positioned adjacent to and at an inwardly spaced distance away from each of said tube plates along the tube axes, and a plurality of additional annular flat guide plates are provided at increasing inward distances away from each of said first-named guide plates, the total area of each additional annular guide plate associated with one of said first-named guide plates becoming progressively smaller than the preceding guide plate in a direction inwardly along the tube axes.
 5. A nested tube reactor as claimed in claim 1 wherein the effective length of the orifices in said guide plate means increases from the center to the outside of the reactor.
 6. A nested tube reactor as claimed in claim 5 wherein said guide plate means contains additional orifices between the orifices surrounding the tubes, the number of said additional orifices per unit area of said plate means increasing from the outside to the center of the reactor. 